操纵GL

操纵GL_LINE_STRIP中的行(manipulating lines in a GL_LINE_STRIP)

我正在制作一个简单的2d绘图程序，其中我有一个顶点数组（比如a1，a2，a3，.....），这些顶点将使用GL_LINE_STRIP绘制。问题是，有3个连续顶点：p1 ，p2，p3，现在我想要if（p2 ==某个特定的顶点值），那么GL_LINE_STRIP应该在p1结束，新的GL_LINE_STRIP从p3开始，忽略p2。 我想在地带的p2休息一下。 我怎么做？？ PS：我尝试在线条的循环中在p2处线宽= 0，但发现由于opengl是一个状态机，我们无法改变glBegin和GLEnd中的宽度。任何其他替代球员???

这里有一些失败的示例代码：

GLfloat thickness; glBegin(GL_LINE_STRIP); for(int i = 0; i < points.size(); i++)//points has all vertices stored...points is an array where each element is a structure containing x and y values { if(points[i].x==randomPoint.x || points[i-1].x==randomPoint.x){//checking if it is equal to p2(i am only checking x coordinate,which is sufficient for me to know that this point is to be excluded) thickness = 0; }else { thickness = 4; } glLineWidth(thickness); glVertex2i(points[i].x, points[i].y); }

I am making a simple 2d drawing program in which i have an array of vertices(say a1,a2,a3,.....) which is to be drawn using GL_LINE_STRIP .Problem is that , say there are 3 consecutive vertices : p1, p2, p3, now i want that if (p2==some specfic vertex value) then the GL_LINE_STRIP should end at p1 and a new GL_LINE_STRIP start at p3, ignoring p2. I want to make a break at p2 in the strip. How do i do that?? PS: I tried making (line width = 0 at p2 in the loop of line strip but found out that since opengl is a state machine, we cant change width inside glBegin and GLEnd. any other alternative guys???

HERE IS SOME FAILED SAMPLE CODE:

GLfloat thickness; glBegin(GL_LINE_STRIP); for(int i = 0; i < points.size(); i++)//points has all vertices stored...points is an array where each element is a structure containing x and y values { if(points[i].x==randomPoint.x || points[i-1].x==randomPoint.x){//checking if it is equal to p2(i am only checking x coordinate,which is sufficient for me to know that this point is to be excluded) thickness = 0; }else { thickness = 4; } glLineWidth(thickness); glVertex2i(points[i].x, points[i].y); }

最满意答案

如果我有正确的问题，你想要在一个顶点停止线条，如果它是一个特定的值，并在下一个顶点开始一个新的。 （如果我误解了，请纠正我）

在要连接的最后一个顶点之后调用glEnd() ，并在想要启动新条带时启动新的glBegin() 。

至于宽度部分，您必须在调用glBegin()之前设置宽度。 如你所说，一条线条（afaik）不能让它的宽度在绘制状态下改变。 您必须结束绘制调用，更改宽度，返回1个顶点并开始新的绘制调用。

If I've got the question right you want to stop the linestrip at a vertex if it is a specific value, and start a new one on the next vertex. (Correct me if I've misunderstood)

Call glEnd() after the last vertex you want to connect and start a new glBegin() when you want to start a new strip.

As for the width part you would have to set the width before the call to glBegin(). A linestrip (afaik) can not have it's width changed in a draw state as you say. You would have to end the draw call, change the width, go 1 vertex back and start a new draw call.